Fig. 3: Asynchronous release fraction is increased in synapses with low release efficacy.

a, b Analysis of the heterogeneity in synchronous and asynchronous release among presynaptic outputs of individual wild type (WT) (a) and Syt1^−/− (b) neurons during a 5 Hz train of 51 action potentials. (i) The relationship between asynchronous release fraction n_A/n_T and the overall vesicular release efficacy n_T among boutons in representative WT (n = 50 boutons) and Syt1^−/− (n = 46 boutons) neurons (see also Supplementary Fig. 8 for more examples). Horizontal dashed lines depict the average fractions of asynchronous release in each cell. Continuous lines, moving averages (20 points span). Vertical dashed lines mark the subdivision of boutons into three terciles with low (T1), intermediate (T2) and high (T3) n_T values. Black dots with error bars depict average values of n_T and n_A/n_T in each tercile (mean ± SEM). (ii) Bar and dot summary plots showing the increase in asynchronous release fraction in boutons with low n_T (mean ± SEM), data from individual cells are connected by dashed lines. (iii) Dependency of n_A/n_T versus n_T averaged among all recorded cells (mean ± SEM). Data are from the same N = 16 wild type and N = 11 Syt1^−/− neurons as in Fig. 2, each recorded neuron contained at least 21 boutons, ** p < 0.01, *** p < 0.001, repeated measures ANOVA (for exact p values, all pairwise multiple comparisons, and further details of statistical analysis see SourceData.xlsx file).